Labour tonight demanded a probe into an £800,000 credit facility provided to Boris Johnson by a distant Canadian cousin.
Party chairwoman Anneliese Dodds wrote to Parliament’s Standards Commissioner calling for an investigation.
It follows weekend reports that, when he was Prime Minister, Mr Johnson had an arrangement with multimillionaire relative Sam Blyth which allowed the ex-Tory leader to fund his lavish lifestyle while in No10 and immediately afterwards.
It later emerged that, at the time the facility was in place, Mr Blyth was in the running for a six-figure job at the British Council, which was seeking a chief executive - and appeared on a "recommendation list”.
Ms Dodds fears it could have looked like a conflict of interest for Mr Johnson.
In a letter, seen exclusively by the Mirror, to Daniel Greenberg, Ms Dodds quotes from rules for MPs, which say: “Holders of public office should not place themselves under any financial or other obligation to outside individuals or organisations that might influence them in the performance of their official duties.”
Ms Dodds claims the former Premier “may have breached this section by entering into an arrangement whereby he was dependent on the generosity of an individual who was, I understand, at the time standing to be chief executive of the British Council”.
She adds: “I’m concerned that, without adequate transparency over this arrangement, it may give the impression that this was a quid pro quo arrangement, something which would fundamentally damage faith in our democratic process.”
Ms Dodds also claims the ex-PM may have broken another rule because the facility was not declared in the Register of Members’ Interests.
“The Code of Conduct states that, even when a gift or a loan in made from a family member (the individual named in the report is a distant cousin), ‘both the possible motive of the giver and the use to which the gift is to be put should be considered’ and that if ‘there is any doubt, the benefit should be registered’,” she writes.
“Clearly the purpose of these rules is to avoid a conflict of interest, both in reality and in perception.
“It is unclear, however, how such an arrangement could possibly be exempt from declaration.”
She calls for “an urgent investigation to establish whether this arrangement has broken the General Principles of Conduct in placing a member in a position where there is a perception of conflict of interests, or the Rules of Conduct by not being appropriately declared”.
Ms Dodds told the Mirror: "Trust in politicians is at an all time low, thanks to the lies, sleaze and erosion of standards that took place under Boris Johnson.
“It is vital for all MPs, from backbenchers to the Prime Minister, to conduct themselves with honesty and transparency, especially in their financial dealings.
“Failing to do so risks damaging that already fragile trust.
“If No10 or the Conservative Party cannot come clean on who Boris Johnson received money from, or how much, or on what terms, then there must be an urgent investigation by the Parliamentary Standards Commissioner.”
Mr Johnson’s spokesman said: “This is nonsense.
“There is no conflict of interest or breach of the MPs’ Code of Conduct.
“There was never any loan made by Sam Blyth.
“Mr Johnson neither knew about nor in any way assisted Mr Blyth in any application for any public position.
“Mr Johnson made all the necessary declarations he was required to make, for example, in the register of ministers' interests.
“At all times he acted on the instructions of officials, the Cabinet Secretary and the Independent Adviser on Ministerial Interests, as the Cabinet Office has confirmed.”
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